mtd: atmel_nand: make PMECC lookup table and offset property optional

If there is no PMECC lookup table stored in ROM, or lookup table offset is
not specified, PMECC driver should build it in DDR by itself.

That make the PMECC driver work for some board which doesn't have PMECC
lookup table in ROM.

The PMECC use the BCH algorithm, so based on the build_gf_tables()
function in lib/bch.c, we can build the Galois Field lookup table.

For more information can refer to section 5.4 of PMECC controller
application note:
http://www.atmel.com/images/doc11127.pdf

Signed-off-by: Josh Wu <[e-mail]>
Cc: [e-mail]
Signed-off-by: Brian Norris <[e-mail]>

Documentation/devicetree/bindings/mtd/atmel-nand.txt

···
 - reg : should specify localbus address and size used for the chip,
 	and hardware ECC controller if available.
 	If the hardware ECC is PMECC, it should contain address and size for
-	PMECC, PMECC Error Location controller and ROM which has lookup tables.
+	PMECC and PMECC Error Location controller.
+	The PMECC lookup table address and size in ROM is optional. If not
+	specified, driver will build it in runtime.
 - atmel,nand-addr-offset : offset for the address latch.
 - atmel,nand-cmd-offset : offset for the command latch.
 - #address-cells, #size-cells : Must be present if the device has sub-nodes
···
   are: 512, 1024.
 - atmel,pmecc-lookup-table-offset : includes two offsets of lookup table in ROM
   for different sector size. First one is for sector size 512, the next is for
-  sector size 1024.
+  sector size 1024. If not specified, driver will build the table in runtime.
 - nand-bus-width : 8 or 16 bus width if not present 8
 - nand-on-flash-bbt: boolean to enable on flash bbt option if not present false
 - Nand Flash Controller(NFC) is a slave driver under Atmel nand flash

drivers/mtd/nand/atmel_nand.c

···
 	bool			has_pmecc;
 	u8			pmecc_corr_cap;
 	u16			pmecc_sector_size;
+	bool			has_no_lookup_table;
 	u32			pmecc_lookup_table_offset;
 	u32			pmecc_lookup_table_offset_512;
 	u32			pmecc_lookup_table_offset_1024;
···
 	return 0;
 }
 
+static inline int deg(unsigned int poly)
+{
+	/* polynomial degree is the most-significant bit index */
+	return fls(poly) - 1;
+}
+
+static int build_gf_tables(int mm, unsigned int poly,
+		int16_t *index_of, int16_t *alpha_to)
+{
+	unsigned int i, x = 1;
+	const unsigned int k = 1 << deg(poly);
+	unsigned int nn = (1 << mm) - 1;
+
+	/* primitive polynomial must be of degree m */
+	if (k != (1u << mm))
+		return -EINVAL;
+
+	for (i = 0; i < nn; i++) {
+		alpha_to[i] = x;
+		index_of[x] = i;
+		if (i && (x == 1))
+			/* polynomial is not primitive (a^i=1 with 0<i<2^m-1) */
+			return -EINVAL;
+		x <<= 1;
+		if (x & k)
+			x ^= poly;
+	}
+	alpha_to[nn] = 1;
+	index_of[0] = 0;
+
+	return 0;
+}
+
+static uint16_t *create_lookup_table(struct device *dev, int sector_size)
+{
+	int degree = (sector_size == 512) ?
+			PMECC_GF_DIMENSION_13 :
+			PMECC_GF_DIMENSION_14;
+	unsigned int poly = (sector_size == 512) ?
+			PMECC_GF_13_PRIMITIVE_POLY :
+			PMECC_GF_14_PRIMITIVE_POLY;
+	int table_size = (sector_size == 512) ?
+			PMECC_LOOKUP_TABLE_SIZE_512 :
+			PMECC_LOOKUP_TABLE_SIZE_1024;
+
+	int16_t *addr = devm_kzalloc(dev, 2 * table_size * sizeof(uint16_t),
+			GFP_KERNEL);
+	if (addr && build_gf_tables(degree, poly, addr, addr + table_size))
+		return NULL;
+
+	return addr;
+}
+
 static int atmel_pmecc_nand_init_params(struct platform_device *pdev,
 					 struct atmel_nand_host *host)
 {
 	struct mtd_info *mtd = &host->mtd;
 	struct nand_chip *nand_chip = &host->nand_chip;
 	struct resource *regs, *regs_pmerr, *regs_rom;
+	uint16_t *galois_table;
 	int cap, sector_size, err_no;
 
 	err_no = pmecc_choose_ecc(host, &cap, &sector_size);
···
 	regs_rom = platform_get_resource(pdev, IORESOURCE_MEM, 3);
 	host->pmecc_rom_base = devm_ioremap_resource(&pdev->dev, regs_rom);
 	if (IS_ERR(host->pmecc_rom_base)) {
-		err_no = PTR_ERR(host->pmecc_rom_base);
-		goto err;
+		if (!host->has_no_lookup_table)
+			/* Don't display the information again */
+			dev_err(host->dev, "Can not get I/O resource for ROM, will build a lookup table in runtime!\n");
+
+		host->has_no_lookup_table = true;
+	}
+
+	if (host->has_no_lookup_table) {
+		/* Build the look-up table in runtime */
+		galois_table = create_lookup_table(host->dev, sector_size);
+		if (!galois_table) {
+			dev_err(host->dev, "Failed to build a lookup table in runtime!\n");
+			err_no = -EINVAL;
+			goto err;
+		}
+
+		host->pmecc_rom_base = (void __iomem *)galois_table;
+		host->pmecc_lookup_table_offset = 0;
 	}
 
 	nand_chip->ecc.size = sector_size;
···
 
 	if (of_property_read_u32_array(np, "atmel,pmecc-lookup-table-offset",
 			offset, 2) != 0) {
-		dev_err(host->dev, "Cannot get PMECC lookup table offset\n");
-		return -EINVAL;
+		dev_err(host->dev, "Cannot get PMECC lookup table offset, will build a lookup table in runtime.\n");
+		host->has_no_lookup_table = true;
+		/* Will build a lookup table and initialize the offset later */
+		return 0;
 	}
 	if (!offset[0] && !offset[1]) {
 		dev_err(host->dev, "Invalid PMECC lookup table offset\n");

drivers/mtd/nand/atmel_nand_ecc.h

···
 #define PMECC_GF_DIMENSION_13			13
 #define PMECC_GF_DIMENSION_14			14
 
+/* Primitive Polynomial used by PMECC */
+#define PMECC_GF_13_PRIMITIVE_POLY		0x201b
+#define PMECC_GF_14_PRIMITIVE_POLY		0x4443
+
 #define PMECC_LOOKUP_TABLE_SIZE_512		0x2000
 #define PMECC_LOOKUP_TABLE_SIZE_1024		0x4000